Add full relay chain + collator tests in CI pipeline

[JoeCap08055]

Feature Description

Details

In the course of upgrading to polkadot-stable2412, an incompatibility was introduced that prevents our collator node from onboarding to the relay chain. Because our CI pipeline only tests parachain functionality with no relay chain (instant-seal or interval-seal build/mode), this was only detected through manual testing. We should develop a test in CI to validate that full parachain + relay chain behaves properly.

How to test (manually)

• Run make run-frequency-docker
  • This brings up 2 relay chain nodes (alice + bob), and 1 Frequency "alice" collator node as Docker containers
  • Registers parachain ID 2000 with the relay chain
  • Onboards the Frequency runtime from the collator node to the relay chain
• Expected results: parachain collator starts forming blocks

Acceptance Criteria

• [ ] Top-level Makefile includes a target to run tests locally for above
• [ ] CI pipeline includes a workflow to test the above setup

Searched for Related Issues

• [x] I have done a search for related issues and either found none, or noted them